Thom
Hyperbaric oxygenation prevents the development of delayed neuropsychological sequelae in mild/moderately severe carbon monoxide poisoning.
Clinical Bottom Line: 1. HBO decreased the incidence of delayed neuropsychological sequelae. 2. The entry level of COHb was not predictive of DNS. 3. All patients with DNS recovered to base-line scores during further follow-up.
Appraised by: Mike Bennett, Dept of Diving and Hyperbaric Medicine Prince of Wales Hospital Sydney; Friday 2nd October 1998
Clinical Scenario: Adult with mild to moderate carbon monoxide poisoning. Three-part Question: In patients with carbon monoxide poisoning, does treatment with HBO in contrast to treatment with NBO, result in a reduction in the incidence of delayed neurological sequelae? Search Terms: Carbon monoxide poisoning/therapy, hyperbaric oxygenation
The Study: Non-blinded randomised controlled trial with intention-to-treat. Exposure to products of combustion and/or high COHb level and/or symptoms and signs suggestive of CO poisoning. Excluded if unconscious at any time or evidence of myocardial compromise. Control group (N = 32; 30 analysed): 100% oxygen via face mask until symptoms resolved, (ave 4.2 hours). Experimental group (N = 33; 30 analysed): 100% oxygen as above until HBO instituted at 2.8ATA for 30 mins, then 2.0ATA for 90 mins, (ave total time 2.1 hours).
The Evidence:
| Outcome | Time to Outcome | Control Group Rate | HBO Group Rate | Relative risk reduction | Absolute risk reduction | Number Needed to Treat |
| Diagnosis of DNS | 4 weeks | 0.233 | 0 | 100% | 0.233 | 4 |
| 95% Confidence Intervals: | 0.082 to 0.384 | 3 to 12 |
Comments: 1. HBO given early (<6 hours from exposure in all cases). 2. All DNS patients eventually recovered. 3. Greatest flaw of the study is that it was not blinded.
Expiry date:August 2022
References: 1. Thom SR, Taber RL, Mendiguren II, Clark JM, Hardy KR, Fisher AB. Delayed neuropsychologic sequelae after carbon monoxide poisoning: prevention by treatment with hyperbaric oxygen.Ann Emerg Med. 1995 Apr;25(4):474-80.
